Los Angeles police detectives said the head may be that of an Armenian-American man in his 40s who had been slain recently, the Los Angeles Times reported. The man had not been identified.
The newspaper said law enforcement sources familiar with the investigation who asked not to be named said two women were hiking with the dog when it came across the head.
The head was found about 3:45 p.m. PST, city police spokeswoman Sara Faden said.
Investigators were looking for more body parts in the vicinity, officials said.